Herd Final Score and Its Relationship to Genetic and Environmental Parameters of Conformation Traits of United States Holsteins

Abstract

First parity conformation scores from 7410 herd rounds of classification were analyzed to determine relationships between genetic and environmental parameters and herd mean for type. Herd rounds were stratified into quintiles according to herd mean for final score. Within each group, REML estimates of sire and error variance were approximated using the tilde-hat method. Average heritability estimates were final score, .21; stature, .36; strength, .28; body depth, .33; angularity, .27; rump angle, .37; rump length, .19; rump width, .26; rear legs (side view), .19; foot angle, .13; fore udder attachment, .24; rear udder height, .23; rear udder width, .20; udder support, .17; udder depth, .31; and teat placement, .27. Heritabilities and genetic and environmental variances were regressed on group mean for final score. For final score, environmental variance decreased at a decreasing rate as group mean final score increased, and genetic variance declined linearly. For most descriptive traits, environmental variance decreased linearly as herd mean final score increased. Linear decreases in genetic variance were significant for foot angle, udder depth, and rump angle. Heritability estimates for final score demonstrated no significant trends as herd mean increased. Positive trends were significant for heritabilities of body depth, angularity, rear udder height, udder support, and teat placement as herd mean final score increased.